24. =The Roman Walls.=--Agricola, in addition to his line of forts between the Forth and the Clyde, had erected detached forts at the mouth of the valleys which issue from the Highlands, in order to hinder the Caledonians from plundering the lower country. In =119= the Emperor Hadrian visited Britain. He was more disposed to defend the Empire than to extend it, and though he did not abandon Agricola's forts, he also built further south a continuous stone wall between the Solway and the Tyne. This wall, which, together with an earthwork of earlier date, formed a far stronger line of defence than the more northern forts, was intended to serve as a second barrier to keep out the wild Caledonians if they succeeded in breaking through the first. At a later time a lieutenant of the Emperor, Antoninus Pius, who afterwards became Emperor himself, connected Agricola's forts between the Forth and Clyde by a continuous earthwork. In =208= the Emperor Severus arrived in Britain, and after strengthening still further the earthwork between the Forth and Clyde, he attempted to carry out the plans of Agricola by conquering the land of the Caledonians. Severus, however, failed as completely as Agricola had failed before him, and he died soon after his return to Eboracum. [Illustration: View of part of the Roman Wall.] [Illustration: Ruins of a Turret on the Roman Wall.] [Illustration: Part of the Roman Wall at Leicester.] [Illustration: Pediment of a Roman temple found at Bath.] 25. =The Roman Province of Britain.=--Very little is known of the history of the Roman province of Britain, except that it made considerable progress in civilisation. The Romans were great road-makers, and though their first object was to enable their soldiers to march easily from one part of the country to another, they thereby encouraged commercial intercourse. Forests were to some extent cleared away by the sides of the new roads, and fresh ground was thrown open to tillage. Mines were worked and country houses built, the remains of which are in some places still to be seen, and bear testimony to the increased well-being of a population which, excepting in the south-eastern part of the island, had at the arrival of the Romans been little removed from savagery. Cities sprang up in great numbers. Some of them were at first garrison towns, like Eboracum, Deva, and Isca Silurum. Others, like Verulamium, near the present St. Albans, occupied the sites of the old stockades once used as places of refuge by the Celts, or, like Lindum, on the top of the hill on which Lincoln Cathedral now stands, were placed in strongly defensible positions. Aquae Sulis, the modern Bath, owes its existence to its warm medicinal springs. The chief port of commerce was Londinium, the modern London. Attempts which have been made to explain its name by the Celtic language have failed, and it is therefore possible that an inhabited post existed there even before the Celts arrived. Its